Color architecture in alert macaque cortex revealed by fMRI

The contribution that different brain areas make to primate color vision, especially in the macaque, is debated. Here we used functional magnetic resonance imaging in the alert macaque, giving a whole brain perspective of color processing in the healthy brain. We identified color-biased and luminance-biased activity and color-afterimage activity. Color-biased activity was found in V1, V2, and parts of V4 and not in V3a, MT, or other dorsal stream areas, in which a luminance bias predominated. Color-biased activity and color-afterimage activity were also found in a region on the posterior bank of the superior temporal sulcus. We review anatomical and physiological studies that describe this region, PITd, and postulate that it is distinct from areas V4 and TEO. When taken together with single-unit studies and lesion studies, our results suggest that color depends on a connected ventral-stream pathway involving at least V1, V2, V4, and PITd.